Some integrated circuit devices, such as data processor cores, can operate in multiple power modes, such as an active or normal power mode and a lower power mode. In an active power mode, a voltage regulator provides a voltage to the processor core that allows the processor core to execute instructions at a normal rate and perform normal operations. In the lower power mode, the voltage regulator provides a retention voltage to the processor core that allows the processor to retain its internal state, but not execute instructions at a normal rate or perform other normal operations. The retention voltage is lower than the voltage provided in the active power mode, thereby allowing the processor core to conserve power. The processor core can enter the low power mode to conserve power while retaining its internal state and retain data stored in memory so that when it returns to the active power mode it is able to continue operations from the state it had when it entered the lower power mode.
An operating system can cause the processor core to enter the lower power mode when certain conditions are met, such as when there are no pending operations at the processor core and no pending operations on the processor bus. However, the accuracy with which the operating system can monitor the conditions is sometimes low. Furthermore, the rate at which the operating system can implement a lower power mode can cause the processor core to remain in the active power mode longer and consume more power than is desirable. Accordingly, there is a need for an improved technique of power management for an integrated circuit device.